1. Field of the Invention
Drills, as a metal or wood working tool, have existed for several years. Such tools typically consist of a shank portion, which may be straight or tapered, and a flute portion terminating in a tip which initially penetrates into the metal work piece to position the cutting tool on the work piece. Flutes may be helical or straight. In either case, however, the flutes extend radially outwardly from the longitudinal axis of the tool and terminate in a peripheral edge which may be sharpened, so as to present a cutting surface to the work piece, be it metal, or wood, or some other composition.
As in any labor intensive manufacturing process, time is of great importance. As the quest for greater efficiency and productivity became the focus of every manufacturer, those whose products required one or more holes to be formed in a work piece sought tools that could do the job faster without sacrifice to quality.
This quest translated, for such manufacturers, into a need for high performance cutting tools in the form of drills. However, speed was only one factor, and the tool had to be not only fast, but had to last through a large number of cycles. Speed, however, begat heat and a greatly increased amount of metal chips at the site of the cut. Heat is destructive of the tool and the process and it was necessary, therefore, to not only cool the cutting surfaces, but to rapidly remove metal chips from the immediate area of the cut.
These needs, early on, seemed to be met by the advent of carbide cutting elements, which, by virtue of their hardness and strength, seemed to remain sharp and relatively impervious to heat for a considerable number of cycles, irrespective of the characteristics of the work piece to be machined.
Furthermore, as long as the machine function was one of drilling a hole of constant diameter, the process of creating a cutting tool, in the form of a twist drill, is relatively easy. When, however, the hole to be cut includes a countersink, multiple diameters, and perhaps one or more lands, the tool becomes complex. Obviously, in order to devise one tool to drill a complex hole, several cutting surfaces would have to be formed along the flute, and at specific angles with one another, to define the precise hole needed.
To this end, makers of tools such as drills were required to form a variety of angularly disposed cutting surfaces on their drills and where a carbide cutting tool was called for, the process became more difficult, in particular because of the difficulty in working with carbide materials which are notoriously tough.
2. Description of Related Prior Art
The cutting tool industry's response to the needs of manufacturers who use their cutting tools, at least to date, has been to either sharpen the flutes on the tool itself, or, where harder cutters are called for, to form a series of carbide elements, typically in opposed pairs, and secure them, in diametric opposition, on the drill.
Exemplification of this latter principal is found in the carbide drills currently made by ARC Cutting Tools, Inc. in which carbide cutting elements having a cutting surface disposed at a specific angle relative to the longitudinal axis of the body of the drill, are affixed to the flutes of a drill, at various positions along the axis of the drill. When the drill is rotated into a work piece, the various surfaces bore out a hole of predetermined configuration in accordance with the manufacturers specification.
There are also several patents which reflect the industry's slavish adherence to these time honored formulae, among them Haque et al. U.S. Pat. No. 4,620,822, and Jodock et al. U.S. Pat. No. 4,605,347, both of which illustrate sharpened flute edges.
Regensburger U.S. Pat. No. 4,480,951, discloses a self tapping screw in which the base portion of a drill bit is secured in the leading edge of the screw and opposed wings are separately attached to the sides of the drill bit. While not itself a cutting tool, but rather a one-time use fastener, Regensburger illustrates the kind of thinking which permeates the industry generally. Several variations on the same theme are shown in FIGS. 6 through 12 of his patent.
Luebbert U.S. Pat. No. 4,093,395 illustrates a twist drill for use with composite materials and includes a carbide tip 11 brazed onto a tool steel body. The tool illustrated lacks the kind of strength necessary to accomplish the tasks capable of being performed by the tool of the present invention for the many reasons discussed in the following Description of a Preferred Embodiment.
Unfortunately, simply hanging a series of cutting elements on the perimeter of a drill, as in the nature of Regensburger, is fraught with problems, such as breaking off of one or more of the elements, irregular and excessive wear of the cutting surfaces, and mispositioning of the elements, and inadequate heat dissipation, all of which can, and do, result in a poor quality, out of tolerance hole in a work piece that may well be ruined as a result.